The overall objective of this project is to elucidate the role of sterol carrier proteins in intracellular transport of cholesterol to and from storage sites, and in mitochondrial utilization of substrate cholesterol for steroidogenesis. Studies are designed to investigate the role of SCP2 in esterification and storage of extracellular and biosynthesized cholesterol, on removal of unesterified cholesterol from lipid storage droplets, ad on transport of cholesterol to the mitochondrial cytochrome P-450 dependent cleavage enzyme (desmolase). For these aims, the experimental models will include isolated cellular organelles (lipid inclusion droplets, mitochondria, smooth endoplasmic reticulum) and intact rat adrenocortical cells. Where feasible, comparative studies will be conducted with adrenocortical cells. Where feasible, comparative studies will be conducted with other small-molecular weight proteins involved in intracellular lipid transport (e.g. phospholipid transfer protein, Z-protein or fatty acid binding protein, SCP1).